Light-emitting diode and manufacturing method thereof

ABSTRACT

A light-emitting diode and the manufacturing method thereof are provided, wherein the light-emitting diode comprises an epitaxial structure, a bonding layer and a composite substrate. The bonding layer located over one side of the epitaxial structure is used for adhering the composite substrate to the epitaxial structure. The composite substrate comprises a patterned silicon layer penetrated through by a plurality of openssilicon, and a metal layer covering the patterned silicon layer, wherein a portion of the metal layer is filled into the opens and contacts the bonding layer.

RELATED APPLICATIONS

The present application is based on, and claims priority from, TaiwanApplication Serial Number 94115424, filed May 12, 2005, the disclosureof which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a light-emitting diode (LED) and themanufacturing method thereof, and more particularly relates to an LEDthat has good thermal conductivity and good processability and themanufacturing method thereof.

BACKGROUND OF THE INVENTION

An LED is composed of an epitaxial structure such as a homo-structure, asingle hetero-structure, a double hetero-structure or a multiple quantumwell. An LED having a p-n junction interface that can emit light withvarious wavelengths has several characteristics, such as a lowelectrical power consumption, low heat generation, long operationallife, small volume, good impact resistance, fast response and excellentstability; thus the LED has been popularly used in electrical appliancesand electronic devices as a light source.

Typically, an LED is composed of an epitaxial structure having asubstrate, an n-type cladding layer formed over the substrate, a p-typecladding layer and an active layer formed between the n-type claddinglayer and the p-type cladding layer. Light is emitted as current flowsthrough the epitaxial structure. The light wavelength can be altered byvarying the composition of the epitaxial structure material.

To improve performance, an LED requires some downstream processes toincrease its brightness, thermal conductivity or the effectiveness ofcurrent diffusion. The downstream processes, such as a cutting process,may require a substrate transferring technology or a wafer bondingtechnology for forming additional substrates made of metal or III-Vsemiconductor materials. Either copper having good thermal conductivityor silicon with good process abilities (for example, with high rigidityand low coefficient of thermal expansion) is appropriate for forming theadditional substrates. However, applying copper or silicon individuallycannot improve both the yield of the downstream processes and theperformance of an LED simultaneously, even though copper has goodthermal conductivity and silicon has good processability. The processyield can be improved with copper due to its high thermal conductivity,but its poor rigidity and large coefficient of thermal expansion createsbad processability, particularly when a thinner copper substrate isrequired. Meanwhile, the performance of an LED can be improved withsilicon since its coefficient of thermal expansion complimentsdownstream processes, but its poor thermal conductivity creates poorprocess yield.

It is desired, therefore, to provide a method for forming an LED havinggood thermal conductivity and good processability so as to improve theyield and performance thereof.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide an LEDhaving good thermal conductivity and good processability. The LEDcomprises an epitaxial structure, a bonding layer and a compositesubstrate. The bonding layer located over one side of the epitaxialstructure is used for adhering the composite substrate to the epitaxialstructure. The composite substrate comprises a patterned silicon layerthat is covered by a metal layer and penetrated by at least one open,wherein the opens are filled in by a portion of the metal layer, suchthat the metal contacts the bonding layer.

Another objective of the present invention is to provide a manufacturingmethod for forming the aforementioned LED to improve the yield andperformance thereof.

First, an epitaxial structure is formed on a first substrate. A secondsubstrate is provided and patterned subsequently to form at least oneopen on a first surface of the second substrate. Then, an adheringprocess is conducted to adhere the first surface of the second substrateto the side of the epitaxial structure away from the first substrate. Aportion of the patterned second substrate is removed to form at leastone through-hole penetrating through the opens, wherein a portion of thebonding layer is exposed through the through-hole. A metal layer is thenformed over the remaining second substrate to fill the through-hole andmake electrical contact with the bonding layer before the firstsubstrate is removed.

Accordingly, the feature of the present invention is to provide acomposite substrate having good thermal conductivity via copper and goodprocessability via silicon, so as to resolve the prior art problems byimproving processing yield and the performance of an LED.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 illustrates a cross-sectional view of an LED structure, inaccordance with the first embodiment of the present invention.

FIG. 2 illustrates a cross-sectional view of an epitaxial structure forforming the LED structure, in accordance with the first embodiment ofthe present invention.

FIG. 3 a illustrates a cross-sectional view of a patterned secondsubstrate for forming the LED structure, in accordance with the firstembodiment of the present invention.

FIG. 3 b illustrates a top view of the second substrate after thepatterning process is conducted, in accordance with the first embodimentof the present invention.

FIG. 4 is a cross-sectional view of the structure after the patternedsecond substrate is adhered to the epitaxial structure, in accordancewith the first embodiment of the present invention.

FIG. 5 is a cross-sectional view of the structure after a portion of thepatterned second substrate is removed, in accordance with the firstembodiment of the present invention.

FIG. 6 is a cross-sectional view of the structure after a metal layer isformed over the patterned silicon layer, in accordance with the firstembodiment of the present invention.

FIG. 7 illustrates a cross-sectional view of an LED structure, inaccordance with the second embodiment of the present invention.

FIG. 8 illustrates a cross-sectional view of an epitaxial structure forforming the LED structure, in accordance with the second embodiment ofthe present invention.

FIG. 9 is a cross-sectional view of the structure after a secondsubstrate is adhered to the epitaxial structure, in accordance with thesecond embodiment of the present invention.

FIG. 10 a is a cross-sectional view of the structure after a portion ofthe second substrate is removed, in accordance with the secondembodiment of the present invention.

FIG. 10 b illustrates a top view of the second substrate after thepatterned silicon layer is formed, in accordance with the secondembodiment of the present invention.

FIG. 11 is a cross-sectional view of the structure after a metal layeris formed over the patterned silicon layer, in accordance with thesecond embodiment of the present invention.

FIG. 12 is a cross-sectional view of the structure after a firstelectrode and a second electrode are formed on the epitaxial structure,in accordance with the first embodiment of the present invention.

FIG. 13 is a cross-sectional view of another structure after a firstelectrode and a second electrode are formed on the epitaxial structure,in accordance with the first embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The feature of the present invention is to provide a composite substratehaving good thermal conductivity via copper and good processability viasilicon, so as to improve processing yield and the performance of anLED.

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description.

FIG. 1 illustrates a cross-sectional view of an LED structure, inaccordance with the first embodiment of the present invention.

The LED comprises an epitaxial structure 102, a bonding layer 104 and acomposite substrate 300. The bonding layer 104 located over one side ofthe epitaxial structure 102 is used for adhering the composite substrate300 to the epitaxial structure 102. The composite substrate 300comprises a patterned silicon layer 106a penetrated through by at leastone open 103 and a metal layer 108 covering the patterned silicon layer106a, wherein a portion of the metal layer 108 is filled in the opens103.

FIG. 2 illustrates a cross-sectional view of an epitaxial structure forforming the LED structure, in accordance with the first embodiment ofthe present invention. According to the first embodiment of the presentinvention, forming the LED structure comprises the following steps:

First, an epitaxial structure 102 is formed on a first substrate 100.The epitaxial structure 102 is formed over the first substrate 100. Invarious embodiments of the present invention, the epitaxial structure102 comprises a homo-structure, a single hetero-structure, a doublehetero-structure, a multiple quantum well or any arbitrary combinationthereof In the present embodiment, the epitaxial structure 102 includesan n-type cladding layer 112 made of AlGaInP, an active layer 114 and ap-type cladding layer 116 made of AlGaInP deposited sequentially overthe first substrate 100 by an epitaxial process, wherein the activelayer 114 is a multiple quantum well made of AlGaInP. In the presentembodiment, the epitaxial structure 102 further comprises a contactlayer 109 formed over the p-type cladding layer 116, and ananti-reflection layer 110 formed over the contact layer 109.

FIG. 3 a illustrates a cross-sectional view of a patterned secondsubstrate 106 for forming the LED structure, in accordance with thefirst embodiment of the present invention. In the present invention, thesecond substrate 106 made of silicon and having a first surface 111 anda second surface 115. Then, a patterning process, such as an etchprocess, is conducted on the fist surface 111 to form at least one open103.

FIG. 3 b illustrates a top view of the second substrate after thepatterning process is conducted. In various embodiments of the presentinvention, the shapes of the opens 103 are circular, triangular,rectangular, polygonal, irregular or any arbitrary combination thereof,and the opens are arranged regularly or irregularly. In the presentembodiment, the opens 103 are circular and arranged regularly.

Next, an adhering process is conducted to adhere the first surface 111of the second substrate 106 to the side of the epitaxial structure 102away from the first substrate 100.

FIG. 4 is a cross-sectional view of the structure after the patternedsecond substrate is adhered with the epitaxial structure, in accordancewith the first embodiment of the present invention. In the presentembodiment, the adhering process is conducted by the following steps.First, a bonding layer 104 is formed on the anti-reflection layer 110 ofthe epitaxial structure 102. For example, a bonding layer 104 includingorganic material, such as B-staged bisbenzocyclobutene (BCB) resin,metal material, such as AuBe/Au alloy, or the combination thereof isformed on the anti-reflection layer 110 of the epitaxial structure 102by a spin coating process. Subsequently, a bonding process follows toadhere the first surface 111 of the patterned second substrate 106 tothe bonding layer 104.

A portion of the patterned second substrate 106 is removed after theadhering process is conducted.

FIG. 5 is a cross-sectional view of the structure after a portion of thepatterned second substrate is removed, in accordance with the firstembodiment of the present invention. In the present embodiment, aportion of the patterned second substrate 106 is removed by an etchprocess or a chemical mechanical polishing process to form at least onethrough-hole penetrating through the opens 103 and exposing a portion ofthe bonding layer 104 through the through-holes. The remaining portionof the patterned second substrate 106 formed as a patterned siliconlayer106 a has a thickness that is substantially between 1 μm and 200 μm.

Then, a metal layer 108 is formed over the patterned silicon layer 106a.

FIG. 6 is a cross-sectional view of the structure after the metal layeris formed over the patterned silicon layer, in accordance with the firstembodiment of the present invention. A sputtering process, anodicoxidation process or the combination thereof forms the metal layer 108.The thickness of the metal layer 108 is substantially between 0.5 μm and100 μm. In addition, a portion of the metal layer 108 is filled into thethrough-holes penetrating through the opens 103 and contacts the bondinglayer 104.

The structure of the metal layer 108 depends on the steps of sputteringprocess selected for forming thereof For example, the metal layer 108can be a single metal layer structure, multi-hetero metal interlacestructure, single layer alloy structure or any combination thereof anddepends on the various sputtering steps, such as co-deposition,interlaced deposition and single deposition, and the material used forthe sputtering process. The material of the metal layer 108 can be Cu,Ni, CuO or Cu/Ni alloy and is deposited over the patterned silicon layer106 a. In the present embodiment, the metal layer 108 is made of copper.The metal layer 108 comprises a single copper structure, a Cu/Niinterlace structure or a Cu/Ni alloy structure.

Next, the first substrate 100 is removed to produce the structureillustrated in FIG. 1.

Another method for forming the LED structure is disclosed by the secondembodiment. The method of the second embodiment is substantially similarto the first embodiment, merely varying in the methods for forming thepatterned silicon layer.

FIG. 7 illustrates a cross-sectional view of an LED structure, inaccordance with the second embodiment of the present invention. The LEDcomprises an epitaxial structure 202, a bonding layer 204 and acomposite substrate 400. The bonding layer 204 located over one side ofthe epitaxial structure 202 is used for adhering the composite substrate400 to the epitaxial structure 202. The composite substrate 300comprises a patterned silicon layer 206 a penetrated by at least oneopen 203 silicon, and a metal layer 208 covering the patterned siliconlayer 206 a, wherein a portion of the metal layer 208 is filled in theopens 203.

FIG. 8 illustrates a cross-sectional view of an epitaxial structure forforming the LED structure, in accordance with the second embodiment ofthe present invention. According to the second embodiment of the presentinvention, forming the LED structure comprises the following steps:

First, an epitaxial structure 202 is formed on a first substrate 200.The epitaxial structure 202 is formed over the first substrate 200. Invarious embodiments of the present invention, the epitaxial structure202 comprises a homo-structure, a single hetero-structure, a doublehetero-structure, a multiple quantum well, or any arbitrary combinationthereof In the present embodiment, the epitaxial structure 202 includesan n-type cladding layer 212 made of AlGaInP, an active layer 214 and ap-type cladding layer 216 made of AlGaInP deposited sequentially overthe first substrate 200 by an epitaxial process, wherein the activelayer 214 is a multiple quantum well made of AlGaInP. In the presentembodiment, the epitaxial structure 202 further comprises a contactlayer 209 formed over the p-type cladding layer 216, and ananti-reflection layer 210 formed over the contact layer 209.

Simultaneously, a second substrate 206 is provided. In the presentinvention, the second substrate 206 is made of silicon and has a firstsurface 211 and a second surface 215. Then, an adhering process isconducted to adhere the first surface 211 of the second substrate 206 tothe side of the epitaxial structure 202 away from the first substrate200.

FIG. 9 is a cross-sectional view of the structure after the secondsubstrate is adhered to the epitaxial structure, in accordance with thesecond embodiment of the present invention. In the present embodiment,the adhering process is conducted by the following steps. First, abonding layer 204 is formed on the anti-reflection layer 210 of theepitaxial structure 202. For example, a bonding layer 204 includingorganic material, such as B-staged bisbenzocyclobutene (BCB) resin,metal material, such as AuBe/Au alloy, or the combination thereof isformed on the anti-reflection layer 210 of the epitaxial structure 202by a spin coating process. Subsequently, a bonding process follows toadhere the first surface 211 of the second substrate 106 to the bondinglayer 204.

A portion of the second substrate 206 is removed after the adheringprocess is conducted.

FIG. 10 a is a cross-sectional view of the structure after a portion ofthe second substrate is removed, in accordance with the secondembodiment of the present invention. In the present embodiment, aportion of the second substrate 206 is removed by an etch process or achemical mechanical polishing process to form at least one penetratingopen 203 exposing a portion of the bonding layer 204. The remainingportion of the patterned second substrate 206 formed as a patternedsilicon layer 206 a has a thickness that is substantially between 1 μmand 200 μm.

FIG. 10 b illustrates a top view of the second substrate after thepatterned silicon layer is formed. In some embodiments of the presentinvention, the shapes of the penetrating opens 203 are circular,triangular, rectangular, polygonal, irregular or any arbitrarycombination thereof, and the penetrating opens 203 are arrangedregularly or irregularly. In the present embodiment, the penetratingopens 203 are circular and arranged regularly.

Next, a metal layer 208 is formed over the patterned silicon layer 206a.

FIG. 11 is a cross-sectional view of the structure after the metal layeris formed over the patterned silicon layer 106 a, in accordance with thesecond embodiment of the present invention. A sputtering process, anodicoxidation process or the combination thereof forms the metal layer 208.The thickness of the metal layer 208 is substantially between 0.5 μm and100 μm. In addition, a portion of the metal layer 208 is filled into thethrough-holes penetrating through the opens 203 and contacts the bondinglayer 204.

The structure of the metal layer 208 depends on the steps of sputteringprocess selected for forming thereof. For example, the metal layer 208is a single metal layer structure, multi-hetero metal interlacestructure, single layer alloy structure or any combination thereofdepending on the various sputtering steps, such as co-deposition,interlaced deposition and single deposition, and the material used forthe sputtering process. The material of the metal layer 208 can be Cu,Ni, CuO or Cu/Ni alloy and is deposited over the patterned silicon layer106 a. In the present embodiment, the metal layer 208 is made of copper.The metal layer 208 comprises a single copper structure, a CuNiinterlace structure or a Cu/Ni alloy structure.

Then, the first substrate 200 is removed to produce the structureillustrated in FIG. 7.

In the preferred embodiments of the present invention, the LED structurefurther comprises a first electrode and a second electrode.

FIG. 12 is a cross-sectional view of the structure after the firstelectrode and the second electrode are formed on the epitaxialstructure, in accordance with the first embodiment of the presentinvention. In the present embodiment, the first electrode 130 and thesecond electrode 140 are located on the epitaxial structure 102 on thesame side of the patterned silicon layer 106 a.

The following steps form the first electrode 130 and the secondelectrode 140:

First, an etch process is conducted from the n-type cladding layer 112downward through the active layer 114 to the p-type cladding layer 116,so that a portion of the p-type cladding layer 116 is exposed. Then, thefirst electrode 130 and the second electrode 140 are formed on then-type cladding layer 112 and the p-type cladding layer 116 respectivelyby a deposition process.

In another preferred embodiment, the first electrode 130 and the secondelectrode 140 are connected on the epitaxial structure 102 andrespectively located on different sides of the patterned silicon layer106 a.

FIG. 13 is a cross-sectional view of another structure after the firstelectrode and the second electrode are formed on the epitaxialstructure, in accordance with the first embodiment of the presentinvention. In the present embodiment, the metal layer 108 acts as thesecond electrode 140, and the first electrode 130 is formed on then-type cladding layer 112 by a deposition process.

Accordingly, the advantage of the present invention is to provide acomposite substrate having good thermal conductivity via copper and goodprocessability via silicon, so as to resolve the prior art problems toimprove the processing yield and performance of an LED.

As is understood by a person skilled in the art, the foregoing preferredembodiments of the present invention are illustrated of the presentinvention rather than limiting of the present invention. It is intendedto cover various modifications and similar arrangements included withinthe spirit and scope of the appended claims, the scope of which shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar structure.

1. A light emitting diode (LED) comprising: an epitaxial structure; abonding layer, located over one side of the epitaxial structure; and acomposite substrate comprising: a patterned silicon layer penetratedthrough by at least one open silicon; and a metal layer covering thepatterned silicon layer, wherein a portion of the metal layer is filledinto the opens and contacts the bonding layer.
 2. The light emittingdiode of claim 1, wherein the epitaxial structure is selected from agroup consisting of a homo-structure, a single hetero-structure, adouble hetero-structure, a multiple quantum well and any arbitrarycombination thereof.
 3. The light emitting diode of claim 1, wherein thebonding layer is selected from a group consisting of organic materials,metal materials and the combination thereof.
 4. The light emitting diodeof claim 3, wherein the bonding layer is selected from B-stagedbisbenzocyclobutene (BCB) resin, AuBe/Au alloy and the combinationthereof
 5. The light emitting diode of claim 1, wherein the metal layeris selected from a group consisting of Cu, Ni, CuO, Cu/Ni alloy and anyarbitrary combination thereof
 6. The light emitting diode of claim 1,wherein the feature of the metal layer is selected from a single metallayer structure, a multi-hetero metal interlace structure, a singlelayer alloy structure and any combination thereof
 7. The light emittingdiode of claim 1, wherein the thickness of the metal layer issubstantially between 0.5 μm and 100 μm.
 8. The light emitting diode ofclaim 1, wherein the patterned silicon layer has a thicknesssubstantially between 1 μm and 200 μm.
 9. The light emitting diode ofclaim 1, wherein the feature of the opens is selected from a groupconsisting of a circle, a triangle, a rectangle, a polygon, an irregularshape and any arbitrary combination thereof.
 10. The light emittingdiode of claim 1, wherein the opens are arranged regularly orirregularly.
 11. The light emitting diode of claim 1 further comprisinga contact layer and an anti-reflection layer formed between the bondinglayer and the epitaxial structure.
 12. The light emitting diode of claim1 further comprising a first electrode and a second electrode contactingthe epitaxial structure, wherein the first electrode and the secondelectrode are located on the same side of the patterned silicon layer13. The light emitting diode of claim 1 further comprising a firstelectrode and a second electrode contacting the epitaxial structure,wherein the first electrode and the second electrode are respectivelylocated on different sides of the patterned silicon layer.
 14. The lightemitting diode of claim 13, wherein the second electrode contacts thepatterned silicon layer.
 15. The light emitting diode of claim 14,wherein the second electrode is the metal layer.
 16. A method of formingan LED comprising: providing a first substrate; forming an epitaxialstructure on the first substrate; providing and patterning a secondsubstrate, to form at least one open on a first surface of the secondsubstrate; conducting an adhering process to adhere the first surface ofthe second substrate to the side of the epitaxial structure away fromthe first substrate; removing a portion of the second substrate to format least one through-hole penetrating through the opens and exposing aportion of the bonding layer through the through-holes. forming a metallayer over the remaining portion of the second substrate, wherein aportion of the metal layer is filled into the through-holes and contactsthe bonding layer; and removing the first substrate.
 17. The method ofclaim 16, wherein the epitaxial structure is selected from a groupconsisting of a homo-structure, a single hetero-structure, a doublehetero-structure, a multiple quantum well and any arbitrary combinationthereof
 18. The method of claim 16, wherein the forming of the epitaxialstructure further comprises forming a contact layer and ananti-reflection layer on the side of the epitaxial structure away fromthe first substrate.
 19. The method of claim 16, wherein the secondsubstrate is patterned by an etch process conducted on the first surfaceof the second substrate.
 20. The method of claim 16, wherein the secondsubstrate is made of silicon.
 21. The method of claim 16, wherein theadhering process comprises: forming a bonding layer on the side of theepitaxial structure away from the first substrate; and adhering thefirst surface of the second substrate to the epitaxial structure withthe bonding layer.
 22. The method of claim 21, wherein the bonding layeris selected from B-staged bisbenzocyclobutene (BCB) resin, AuBe/Au alloyand the combination thereof
 23. The method of claim 16, wherein themethod for removing a portion of the second substrate is selected from agroup consisting of an etch process, a chemical mechanical polishingprocess and the combination thereof.
 24. The method of claim 16, whereinthe method for forming the metal layer is selected from a groupconsisting of a sputtering process, anodic oxidation process and thecombination thereof.
 25. The method of claim 16, further comprisingforming a first electrode and a second electrode contacting theepitaxial structure.
 26. The method of claim 25, wherein the firstelectrode and the second electrode are located on the same side of thesecond substrate.
 27. The method of claim 25, wherein the firstelectrode and the second electrode are respectively located on differentsides of the second substrate.
 28. A method of forming an LEDcomprising: providing a first substrate; forming an epitaxial structureon the first substrate; providing a second substrate, wherein the secondsubstrate has a first surface and a second surface; conducting anadhering process to adhere the first surface of the second substrate tothe side of the epitaxial structure away from the first substrate;removing a portion of the second substrate to form at least onepenetrating open and exposing a portion of the bonding layer through thepenetrating opens. forming a metal layer over the remaining portion ofthe second substrate, wherein a portion of the metal layer is filledinto the penetrating opens and contacts the bonding layer; and removingthe first substrate.
 29. The method of claim 28, wherein the epitaxialstructure is selected from a group consisting of a homo-structure, asingle hetero-structure, a double hetero-structure, a multiple quantumwell and any arbitrary combination thereof.
 30. The method of claim 28,wherein the forming of the epitaxial structure further comprises forminga contact layer and an anti-reflection layer on the side of theepitaxial structure away from the first substrate.
 31. The method ofclaim 28, wherein the portion of the second substrate is removed by anetch process conducted on the first surface of the second substrate. 32.The method of claim 28, wherein the second substrate is made of silicon.33. The method of claim 28, wherein the adhering process comprises:forming a bonding layer on the side of the epitaxial structure away fromthe first substrate; and adhering the first surface of the secondsubstrate to the epitaxial structure with the bonding layer.
 34. Themethod of claim 33, wherein the bonding layer is selected from B-stagedbisbenzocyclobutene (BCB) resin, AuBe/Au alloy and the combinationthereof
 35. The method of claim 28, wherein the method for removing aportion of the second substrate is selected from a group consisting ofan etch process, a chemical mechanical polishing process and thecombination thereof.
 36. The method of claim 28, wherein the method forforming the metal layer is selected from a group consisting of asputtering process, an anodic oxidation process and the combinationthereof.
 37. The method of claim 28, further comprising forming a firstelectrode and a second electrode contacting the epitaxial structure. 38.The method of claim 37, wherein the first electrode and the secondelectrode are located on the same side of the second substrate.
 39. Themethod of claim 37, wherein the first electrode and the second electrodeare respectively located on different sides of the second substrate.